1. Field of the Invention
The present invention relates to containers, particularly containers for foodstuffs. More specifically, the present invention is directed to a pull tab system of the easy open type, and methods for manufacturing such easy open pull tabs.
2. Description of the Prior Art
There are a wide variety of easy-open pull tab configurations known in the prior art. Many of these designs and configurations are adapted for a specific use, or in conjunction with a specific metal gauge. Generally, however, there are two types of easy open pull tabs, which can be categorized by the manner in which each functions.
The first category includes those easy open pull tabs designed with a solid, attached rivet hole panel so as to fracture a vent score (commonly referred to as a "moustache", because of its shape) in order to create a fulcrum point for the tab to turn as it is lifted higher above the plane of the end panel. The nose then pierces the score line of the end panel for easy removal.
The second category of easy open pull tab systems are designed with a rivet hole panel independent of the tab body on three sides, but attached to the side opposed to the tab nose. The attached side becomes the fulcrum point between the tab body and the rivet hole.
Typically, pull tab systems are fabricated from flat metal stock using conventional metal stamping and forming techniques. Because large quantities of the pull tabs must be manufactured at one time, it is customary to stamp the tabs in flat strips, permitting the tabs to remain attached to the strip via so called "carrier lugs", which are simply portions of the metal which are not removed until near the end of the fabrication sequence. Heretofore, carrier lugs have been positioned at both ends of the pull tab configuration, usually at the nose portion and along both sides; in some cases, prior art easy open pull tabs have been constructed without carrier lugs being located along the pull ring portion, in order to avoid any sharp edges which might cause injury to the consumer while the pull tab ring is being used for opening.
It is also known to fabricate pull tabs with rivet holes having a six-sided (hexagon) shape, to lock the rivet in the hole after crimping.
Prior art patents which generally describe easy open pull tab arrangements and methods for manufacturing include the following: U.S. Pat. Nos. 3,850,124 to Brown; 4,026,226 to Hahn, et al; and 4,130,074 to Cudzik.